Sunset South Basin
Sunset South Basin is an earth dam located in San Francisco County, California, built in 1960. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Sunset South Basin
The primary purpose of Sunset South Basin is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City And County Of San Francisco (local government). It impounds the Offstream near San Francisco.
The dam stands 34 feet tall and stretches 980 feet across, creates a reservoir covering 12 acres, and has a maximum storage capacity of 268 acre-feet. Completed in 1960, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 05/13/2025.
At 34 feet, this dam is taller than 80% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The California dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | California |
| County | San Francisco |
| Nearest City | San Francisco |
| River/Stream | Offstream |
| Coordinates | 37.74980, -122.48550 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 34 ft |
| Dam Height | 34 ft |
| Dam Length | 980 ft |
| Year Completed | 1960 (66 years old) |
Storage & Hydraulics
| NID Storage | 268 acre-ft |
| Max Storage | 268 acre-ft |
| Surface Area | 12 acres |
Ownership & Safety
| Purpose | Water Supply |
| Owner | City and County of San Francisco |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 05/13/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | CA00136 |
| Federal ID | CA00136 |
| More Info | State Dam Safety Program |